Lydford Law is, punish first and try afterwards. Lydford, in the county of Devon, was a
fortified town, in which was an ancient castle, where were held the courts of the Duchy
of Cornwall. Offenders against the stannary laws were confined before trial in
a dungeon so loathsome and dreary that it gave rise to the proverb referred to. The castle
was destroyed by the Danes

"Stannery" sounds related to Stannum = tin. I wonder wha those laws could have been.

Very interesting URL about tin: http://www.chycor.co.uk/tourism/tolgus/page2.htm